U.S. patent number 8,851,579 [Application Number 13/578,342] was granted by the patent office on 2014-10-07 for vehicle brake device and vehicle brake device control method.
This patent grant is currently assigned to Honda Motor Co., Ltd.. The grantee listed for this patent is Kunimichi Hatano, Arata Inoue, Takashi Nishioka, Naoto Ohkubo. Invention is credited to Kunimichi Hatano, Arata Inoue, Takashi Nishioka, Naoto Ohkubo.
United States Patent |
8,851,579 |
Ohkubo , et al. |
October 7, 2014 |
Vehicle brake device and vehicle brake device control method
Abstract
In a BBW type vehicle brake device, first and second fluid paths
that are connected to each other are both connected to a slave
cylinder with a simple structure that is equipped with a single
fluid pressure chamber, thereby enabling wheel cylinders having two
lines to be operated and eliminating the need for a complicated
tandem type slave cylinder. When the slave cylinder becomes
inoperable due to malfunction of the power supply, by opening first
and second master cut valves and closing the communication control
valve, braking is carried out by means of brake fluid pressure
generated by a master cylinder. In this process, since the
interconnection between the first and second fluid paths is blocked
by closing the communication control valve, even if the wheel
cylinder of one of the brake lines suffers from a liquid leakage
malfunction, the other remained brake line is enabled to ensure a
braking force.
Inventors: |
Ohkubo; Naoto (Wako,
JP), Nishioka; Takashi (Wako, JP), Inoue;
Arata (Wako, JP), Hatano; Kunimichi (Wako,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Ohkubo; Naoto
Nishioka; Takashi
Inoue; Arata
Hatano; Kunimichi |
Wako
Wako
Wako
Wako |
N/A
N/A
N/A
N/A |
JP
JP
JP
JP |
|
|
Assignee: |
Honda Motor Co., Ltd. (Tokyo,
JP)
|
Family
ID: |
44506810 |
Appl.
No.: |
13/578,342 |
Filed: |
February 23, 2011 |
PCT
Filed: |
February 23, 2011 |
PCT No.: |
PCT/JP2011/053928 |
371(c)(1),(2),(4) Date: |
August 10, 2012 |
PCT
Pub. No.: |
WO2011/105405 |
PCT
Pub. Date: |
September 01, 2011 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
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US 20120306260 A1 |
Dec 6, 2012 |
|
Foreign Application Priority Data
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|
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|
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Feb 26, 2010 [JP] |
|
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2010-042928 |
|
Current U.S.
Class: |
303/14;
303/114.1; 303/113.4; 303/113.2; 303/115.2 |
Current CPC
Class: |
B60T
8/4081 (20130101); B60T 13/662 (20130101); B60T
13/686 (20130101); B60T 7/042 (20130101); B60T
8/266 (20130101) |
Current International
Class: |
B60T
13/58 (20060101); B60T 11/20 (20060101) |
Field of
Search: |
;303/14,114.1,113.4,115.4,116.1,115.2,3,6.01,112.13,115.1,11,13,157,158 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
02060867 |
|
Mar 1990 |
|
JP |
|
2006-264675 |
|
Oct 2006 |
|
JP |
|
2008-230362 |
|
Oct 2008 |
|
JP |
|
2009-161130 |
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Jul 2009 |
|
JP |
|
Primary Examiner: Momper; Anna
Assistant Examiner: Aung; San
Attorney, Agent or Firm: Carrier Blackman & Associates,
P.C. Blackman; William D. Carrier; Joseph P.
Claims
The invention claimed is:
1. A vehicle brake device comprising: a master cylinder that is
operated by a brake pedal to generate brake fluid pressure for two
fluid supply lines, a stroke simulator that is connected to at
least one output port of the master cylinder and into which is
introduced a brake fluid from the master cylinder, a first fluid
path that provides a connection between a first fluid pressure
chamber of the master cylinder and a wheel cylinder of a first one
of said fluid supply lines, a second fluid path that provides a
connection between a second fluid pressure chamber of the master
cylinder and a wheel cylinder of a second one of said fluid supply
lines, a slave cylinder that is connected to the first fluid path
and generates a brake fluid pressure by means of the driving force
of an actuator, first and second master cut valves that are
provided in the first and second fluid paths respectively on an
upstream side relative to the slave cylinder and can block
communication between the master cylinder and the wheel cylinders
of the first and second lines, a third fluid path that provides
communication between the first and second fluid paths on a
downstream side relative to the first and second master cut valves,
and a communication control valve that is provided in the third
fluid path and, when closed, blocks fluid communication between the
first and second fluid paths via the third fluid path, wherein the
communication control valve is placed in communication with the
slave cylinder at all times via only one of the first and second
fluid paths.
2. The vehicle brake device according to claim 1, wherein the slave
cylinder comprises restricting means that restricts expansion of
the volume of a fluid pressure chamber of the slave cylinder when a
fluid pressure is externally applied to the fluid pressure
chamber.
3. The vehicle brake device according to claim 1, wherein the
device comprises an auxiliary cut valve that is provided in at
least one of the first and second fluid paths on a downstream side
relative to the third fluid path and that can block the brake fluid
pressure from the slave cylinder, and a pressure reduction valve
that is provided in each wheel cylinder on a downstream side
relative to the auxiliary cut valve and can release the brake fluid
pressure from the slave cylinder into a reservoir.
4. The vehicle brake device according to claim 1, wherein a degree
of opening of the communication control valve is adjustable.
5. The vehicle brake device according to claim 3, wherein the
device comprises a first fluid pressure sensor that detects a brake
fluid pressure generated by the master cylinder and a second fluid
pressure sensor that detects a brake fluid pressure of the third
fluid path or the first and second fluid paths between the first
and second master cut valves and the auxiliary cut valve, the
second fluid pressure sensor being provided in the second fluid
path.
6. A vehicle brake device control method for controlling operation
of the vehicle brake device according to claim 1, the method
comprising a step of transmitting, in a state in which the
communication control valve is closed, the master cut valve
disposed in one fluid path, on the slave cylinder side, of the
first and second fluid paths is closed, and the master cut valve in
the other fluid path is opened, a brake fluid pressure generated by
the slave cylinder to the fluid path on the slave cylinder side of
the first and second fluid paths.
7. A vehicle brake device control method for controlling the
operation of the vehicle brake device according to claim 3, the
method comprising a step of operating the slave cylinder in a state
in which the communication control valve is opened, to generate a
first brake fluid pressure, and a step of opening the pressure
reduction valve and reducing the brake fluid pressure of the wheel
cylinder of at least one of the first and second lines to a second
brake fluid pressure, which is lower than the first brake fluid
pressure.
8. The vehicle brake device according to claim 2, wherein the
device comprises an auxiliary cut valve that is provided in at
least one of the first and second fluid paths on a downstream side
relative to the third fluid path and can block the brake fluid
pressure from the slave cylinder, and a pressure reduction valve
that is provided in each wheel cylinder on a downstream side
relative to the auxiliary cut valve and can release the brake fluid
pressure from the slave cylinder into a reservoir.
9. The vehicle brake device according to claim 2, wherein a degree
of opening of the communication control valve is adjustable.
10. The vehicle brake device according to claim 3, wherein a degree
of opening of the communication control valve is adjustable.
11. The vehicle brake device according to claim 1, wherein the
slave cylinder has only a single piston and has only a single fluid
pressure chamber formed therein proximate said single piston.
12. A vehicle brake device comprising: a master cylinder that is
operated by a brake pedal to generate brake fluid pressure for two
fluid supply lines, a stroke simulator that is selectively
connectable to at least one output port of the master cylinder, and
into which is introduced a brake fluid from the master cylinder, a
first one of said fluid supply lines providing a first fluid path
that provides a connection between a first fluid pressure chamber
of the master cylinder and a first wheel cylinder, a second one of
said fluid supply lines providing a second fluid path that provides
a connection between a second fluid pressure chamber of the master
cylinder and a second wheel cylinder, a slave cylinder that is
connected to the first fluid path and which is operable to
selectively generate a brake fluid pressure by means of the driving
force of an actuator, said slave cylinder having only a single
piston and having a single fluid pressure chamber formed therein
proximate said single piston, first and second master cut valves
that are provided in the first and second fluid paths respectively
on an upstream side relative to the slave cylinder, and that are
operable to selectively block communication between the master
cylinder and the first and second wheel cylinders, a third fluid
path that selectively provides communication between the first and
second fluid paths on a downstream side relative to the first and
second master cut valves, and a communication control valve that is
provided in the third fluid path and, when closed, blocks fluid
communication between the first and second fluid paths via the
third fluid path, wherein the communication control valve is placed
in fluid communication with the slave cylinder, without any other
valve interposed therebetween.
13. The vehicle brake device according to claim 12, wherein the
slave cylinder comprises a ball screw mechanism that restricts
expansion of the volume of the single fluid pressure chamber of the
slave cylinder when a fluid pressure is externally applied to the
fluid pressure chamber.
14. The vehicle brake device according to claim 12, wherein the
brake device further comprises: an auxiliary cut valve that is
provided in at least one of the first and second fluid paths on a
downstream side relative to the third fluid path, said auxiliary
cut valve selectively operable to block the brake fluid pressure
from the slave cylinder, and a pressure reduction valve that is
provided in each wheel cylinder on a downstream side relative to
the auxiliary cut valve, said pressure reduction valve operable to
selectively release the brake fluid pressure from the slave
cylinder into a reservoir.
15. The vehicle brake device according to claim 12, wherein a
degree of opening of the communication control valve is
adjustable.
16. The vehicle brake device according to claim 14, wherein the
brake device further comprises a first fluid pressure sensor that
detects a brake fluid pressure generated by the master cylinder,
and a second fluid pressure sensor that detects a brake fluid
pressure of the third fluid path or the first and second fluid
paths between the first and second master cut valves and the
auxiliary cut valve, the second fluid pressure sensor being
provided in the second fluid path.
Description
TECHNICAL FIELD
The present invention relates to a so-called BBW (brake by wire)
type vehicle brake device that converts a driver's brake pedal
operation into an electrical signal and operates a wheel cylinder
by means of a brake fluid pressure generated by a slave cylinder
that is controlled based on the electrical signal, and a control
method therefor.
BACKGROUND ART
With regard to such a BBW type vehicle brake device, an arrangement
that includes a tandem type master cylinder, a tandem type slave
cylinder, a wheel cylinder of a first line, and a wheel cylinder of
a second line, connects a first fluid pressure chamber of the
master cylinder to the wheel cylinder of the first line via a first
fluid pressure chamber of the slave cylinder, connects a second
fluid pressure chamber of the master cylinder to the wheel cylinder
of the second line via a second fluid pressure chamber of the slave
cylinder, operates the wheel cylinders of the first and second
lines by means of a brake fluid pressure generated by the slave
cylinder when the system is normal, and operates the wheel
cylinders of the first and second lines by means of a brake fluid
pressure generated by the master cylinder when there is an
abnormality of the system is known from Patent Document 1
below.
PRIOR ART DOCUMENTS
Patent Documents
Patent Document 1: Japanese Patent Application Laid-open No.
2009-161130
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
However, in the above-mentioned conventional arrangement, since the
slave cylinder needs to be provided with the first and second fluid
pressure chambers corresponding to the wheel cylinder of the first
line and the wheel cylinder of the second line, there is the
problem that the structure of the slave cylinder becomes
complicated, which contributes to an increase in cost. If in order
to solve this problem the arrangement is such that a brake fluid
pressure is supplied from a slave cylinder provided with a single
fluid pressure chamber to the wheel cylinders of the first and
second lines, when the slave cylinder malfunctions and the wheel
cylinder is operated by means of a brake fluid pressure generated
by the master cylinder, if a malfunction such as liquid leakage
occurs in the wheel cylinder of one of the first and second lines,
there is a possibility that the braking force of the wheel
cylinders of both the first and second lines will be lost.
The present invention has been accomplished in light of the
above-mentioned circumstances, and it is an object thereof to
provide a BBW type brake device in which, when one of two brake
lines malfunctions, backup can be carried out by a slave cylinder
with a simple structure that is equipped with a single fluid
pressure chamber.
Means for Solving the Problems
In order to attain the above object, according to a first aspect of
the present invention, there is provided a vehicle brake device
comprising a master cylinder that is operated by a brake pedal to
generate brake fluid pressure for two lines, a stroke simulator
that is connected to at least one output port of the master
cylinder and into which is introduced a brake fluid from the master
cylinder, a first fluid path that provides a connection between a
first fluid pressure chamber of the master cylinder and a wheel
cylinder of a first line, a second fluid path that provides a
connection between a second fluid pressure chamber of the master
cylinder and a wheel cylinder of a second line, a slave cylinder
that is connected to the first fluid path and generates a brake
fluid pressure by means of the driving force of an actuator, first
and second master cut valves that are provided in the first and
second fluid paths respectively on an upstream side relative to the
slave cylinder and can block communication between the master
cylinder and the wheel cylinders of the first and second lines, a
third fluid path that provides communication between the first and
second fluid paths on a downstream side relative to the first and
second master cut valves, and a communication control valve that
can block the third fluid path.
Further, according to a second aspect of the present invention, in
addition to the first aspect, the slave cylinder comprises
restricting means that restricts expansion of the volume of a fluid
pressure chamber of the slave cylinder when a fluid pressure is
externally applied to the fluid pressure chamber.
Furthermore, according to a third aspect of the present invention,
in addition to the first or second aspect, the device comprises an
auxiliary cut valve that is provided in at least one of the first
and second fluid paths on a downstream side relative to the third
fluid path and can block the brake fluid pressure from the slave
cylinder, and a pressure reduction valve that is provided in each
wheel cylinder on a downstream side relative to the auxiliary cut
valve and can release the brake fluid pressure from the slave
cylinder into a reservoir.
Moreover, according to a fourth aspect of the present invention, in
addition to any one of the first to third aspects, a degree of
opening of the communication control valve is adjustable.
Further, according to a fifth aspect of the present invention, in
addition to the third aspect, the device comprises a first fluid
pressure sensor that detects a brake fluid pressure generated by
the master cylinder and a second fluid pressure sensor that detects
a brake fluid pressure of the third fluid path or the first and
second fluid paths between the first and second master cut valves
and the auxiliary cut valve, the second fluid pressure sensor being
provided in the second fluid path.
Furthermore, according to a sixth aspect of the present invention,
there is provided a vehicle brake device control method for
controlling operation of the vehicle brake device according to the
first aspect, the method comprising a step of transmitting, in a
state in which the communication control valve is closed, the
master cut valve disposed in one fluid path, on the slave cylinder
side, of the first and second fluid paths is closed, and the master
cut valve in the other fluid path is opened, a brake fluid pressure
generated by the slave cylinder to the fluid path on the slave
cylinder side of the first and second fluid paths.
Moreover, according to a seventh aspect of the present invention,
there is provided a vehicle brake device control method for
controlling the operation of the vehicle brake device according to
the third aspect, the method comprising a step of operating the
slave cylinder in a state in which the communication control valve
is opened, to generate a first brake fluid pressure, and a step of
opening the pressure reduction valve and reducing the brake fluid
pressure of the wheel cylinder of at least one of the first and
second lines to a second brake fluid pressure, which is lower than
the first brake fluid pressure.
A first output port 21 of an embodiment corresponds to the output
port of the present invention, an in-valve 52 of the embodiment
corresponds to the auxiliary cut valve of the present invention,
and an out-valve 54 of the embodiment corresponds to the pressure
reduction valve of the present invention.
Effects of the Invention
In accordance with the first aspect of the present invention, in a
normal situation, the first and second fluid paths that are
connected to each other via the third fluid path are both connected
to the slave cylinder by opening the communication control valve
while enabling brake pedal stroke by means of the stroke simulator
in a state in which the first and second master cut valves are
closed, thus enabling the wheel cylinders of the first and second
lines to be operated by means of brake fluid pressure generated by
the slave cylinder and thereby eliminating the need for a tandem
type slave cylinder and simplifying the structure. Furthermore,
when the slave cylinder becomes inoperable, by opening the first
and second master cut valves and closing the communication control
valve the wheel cylinders of the first and second lines can each be
operated via the first and second fluid paths by means of brake
fluid pressure generated by the first and second fluid pressure
chambers of the master cylinder. In this process, since it is
possible to block the interconnection between the first and second
fluid paths by closing the communication control valve provided in
the third fluid path, even if the wheel cylinder of one of the
first and second lines suffers from a liquid leakage malfunction,
operation of the wheel cylinder of the other line is enabled to
thus ensure a minimum necessary braking force.
Furthermore, in accordance with the second aspect of the present
invention, when fluid pressure is externally applied to the fluid
pressure chamber of the slave cylinder, since expansion of the
volume of the fluid pressure chamber is restricted by the
restricting means, it is possible to prevent the brake fluid
pressure from being decreased due to expansion of the volume of the
fluid pressure chamber of the slave cylinder when the wheel
cylinder is operated by means of brake fluid pressure generated by
the master cylinder when the slave cylinder malfunctions.
Moreover, in accordance with the third aspect of the present
invention, since the auxiliary cut valve, which can block the brake
fluid pressure from the slave cylinder, is provided in the fluid
path of at least one of the first and second fluid paths on the
downstream side relative to the third fluid path, and the pressure
reduction valve, which can release the brake fluid pressure from
the slave cylinder into the reservoir, is provided for each wheel
cylinder on the downstream side relative to the auxiliary cut
valve, it is possible to individually reduce any brake fluid
pressure generated by the slave cylinder and transmit it to the
respective wheel cylinder, thereby independently controlling the
brake fluid pressure acting on each slave cylinder and giving ABS
operation or VSA operation.
Furthermore, in accordance with the fourth aspect of the present
invention, since the degree of opening of the communication control
valve is made adjustable, it is possible to reduce the brake fluid
pressure that is to be transmitted to the second fluid path
connected to the first fluid path via the communication control
valve relative to the brake fluid pressure that is generated by the
slave cylinder and transmitted to the first fluid path, thereby
varying the brake fluid pressures acting on the wheel cylinders of
the first and second lines.
Moreover, in accordance with the fifth aspect of the present
invention, since there are provided the first fluid pressure sensor
for detecting the brake fluid pressure generated by the master
cylinder and the second fluid pressure sensor for detecting the
brake fluid pressure of the third fluid path or the first and
second fluid paths between the first and second master cut valves
and the auxiliary cut valve, and the second fluid pressure sensor
is provided not in the first fluid path directly connected to the
slave cylinder but in the second fluid path connected to the slave
cylinder via the communication control valve, when the
communication control valve is closed and connection between the
first and second fluid paths is blocked, it is possible to detect
the brake fluid pressure of the first fluid path by means of the
first fluid pressure sensor and detect the brake fluid pressure of
the second fluid path by means of the second fluid pressure
sensor.
Furthermore, in accordance with the sixth aspect of the present
invention, since the brake fluid pressure generated by the slave
cylinder is transmitted, among the first and second fluid paths, to
the fluid path on the slave cylinder side in a state in which the
communication control valve is closed, the master cut valve
disposed, among the first and second fluid paths, in the fluid path
on the slave cylinder side is closed, and the master cut valve of
the other fluid path is opened; when a malfunction such as liquid
leakage occurs in the wheel cylinder of one of the first and second
lines, it is possible to supply brake fluid pressure from the
master cylinder to the wheel cylinder of the other line, and when a
malfunction such as liquid leakage occurs in the wheel cylinder of
the other of the first and second lines, it is possible to supply
brake fluid pressure from the slave cylinder to the wheel cylinder
of the one line.
Moreover, in accordance with the seventh aspect of the present
invention, since the slave cylinder is operated to generate the
first brake fluid pressure in a state in which the communication
control valve is opened and the first and second fluid paths are
connected to each other, and the brake fluid pressure of the wheel
cylinder of at least one of the first and second lines is reduced
to the second brake fluid pressure, which is lower than the first
brake fluid pressure, by opening the pressure reduction valve, it
is possible to transmit different brake fluid pressures to the
respective wheel cylinders and individually control the braking
force of each wheel.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a fluid pressure circuit diagram (when a power supply is
OFF) of a vehicle brake device. (first embodiment)
FIG. 2 is a diagram for explaining the operation when braking
normally or when regeneratively braking (first embodiment)
FIG. 3 is a diagram for explaining the operation when there is ABS
control. (first embodiment)
FIG. 4 is a diagram for explaining the operation when there is VSA
control. (first embodiment)
FIG. 5 is a diagram for explaining the operation when there is a
malfunction in a fluid path. (first embodiment)
FIG. 6 is a diagram for explaining the operation when there is a
malfunction in the power supply. (first embodiment)
EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS
11 Master cylinder 12 Brake pedal 17 First fluid pressure chamber
19 Second fluid pressure chamber 21 First output port (output port)
26, 27 Wheel cylinder of first line 30, 31 Wheel cylinder of second
line 32 First master cut valve 33 Second master cut valve 35 Stroke
simulator 41 Communication control valve 42 Slave cylinder 43
Actuator 46 Ball screw mechanism (restricting means) 50 Fluid
pressure chamber 52 In-valve (auxiliary cut valve) 53 Reservoir 54
Out-valve (pressure reduction valve) Pa to Pd First fluid path Qa
to Qd Second fluid path Rc Third fluid path Sa First fluid pressure
sensor Sb Second fluid pressure sensor
MODE FOR CARRYING OUT THE INVENTION
A mode for carrying out the present invention is explained below by
reference to FIG. 1 to FIG. 6.
First Embodiment
As shown in FIG. 1, a tandem type master cylinder 11 includes a
first piston 14 and a second piston 15 disposed in front thereof,
the first piston 14 being connected via a push rod 13 to a brake
pedal 12 operated by a driver, a first fluid pressure chamber 17
housing a return spring 16 is defined between the first piston 14
and the second piston 15, and a second fluid pressure chamber 19
housing a return spring 18 is defined in front of the second piston
15. The first fluid pressure chamber 17 and the second fluid
pressure chamber 19, which can communicate with a reservoir 20,
include a first output port 21 and a second output port 22
respectively, the first output port 21 being connected to for
example wheel cylinders 26 and 27 of disk brake devices 24 and 25
of left and right rear wheels (first line) via a fluid path Pa, a
fluid path Pb, a hydraulic modulator 23, and fluid paths Pc and Pd,
and the second output port 22 being connected to for example wheel
cylinders 30 and 31 of disk brake devices 28 and 29 of left and
right front wheels (second line) via a fluid path Qa, a fluid path
Qb, the hydraulic modulator 23, and fluid paths Qc and Qd.
In this specification, the upstream side of the fluid paths Pa to
Pd and the fluid paths Qa to Qd means the master cylinder 11 side,
and the downstream side means the wheel cylinder 26, 27; 30, 31
side.
A first master cut valve 32, which is a normally open
electromagnetic valve, is disposed between the fluid paths Pa and
Pb, and a second master cut valve 33, which is a normally open
electromagnetic valve, is disposed between the fluid paths Qa and
Qb. Connected via a simulator valve 34, which is a normally closed
electromagnetic valve, to fluid paths Ra and Rb that branch from
the fluid path Pa on the upstream side of the first master cut
valve 32 is a stroke simulator 35. The stroke simulator 35 is
formed by slidably fitting into a cylinder 36 a piston 38 urged by
a spring 37, and a fluid pressure chamber 39 formed on the side of
the piston 38 opposite to the spring 37 communicates with the third
fluid path Rb. Connected in parallel to the simulator valve 34 is a
check valve 40 that only permits brake fluid to flow from the
stroke simulator 35 side to the fluid path Pa side.
A communication control valve 41, which is a normally closed
electromagnetic valve, is disposed in a third fluid path Rc that
connects to each other the fluid path Pb and the fluid path Qb on
the downstream side of the first and second master cut valves 32
and 33, and a slave cylinder 42 is connected to a fluid path Rd
branching from the fluid path Pb. An actuator 43 for operating the
slave cylinder 42 transmits rotation of an electric motor 44 to a
ball screw mechanism 46 via a gear train 45. The slave cylinder 42
includes a cylinder main body 47 that is connected to the reservoir
20 of the master cylinder 11 via a fluid path Re, and a piston 48
that is slidably fitted into the cylinder main body 47 is urged by
a return spring 49 in the backward direction. When the piston 48 is
driven by the ball screw mechanism 46 of the actuator 43 in the
forward direction, brake fluid pressure generated in a fluid
pressure chamber 50 is transmitted to the fluid path Rd via an
output port 51.
The structure of the hydraulic modulator 23, which is provided with
ABS (antilock brake system) and VSA (vehicle stability assist)
functions, is known, and the same structure is employed for the
line of the disk brake devices 24 and 25 of the left and right rear
wheels and the line of the disk brake devices 28 and 29 of the left
and right front wheels. The line of the disk brake devices 24 and
25 of the left and right rear wheels is explained as being
representative thereof; in-valves 52 and 52, which are a pair of
normally open electromagnetic valves, are disposed between the
fluid path Pb and the fluid paths Pc and Pd, and out-valves 54 and
54, which are normally closed electromagnetic valves, are disposed
between a reservoir 53 and the fluid paths Pc and Pd on the
downstream side of the in-valves 52 and 52. A hydraulic pump 55 is
disposed between the reservoir 53 and the fluid path Pb, this
hydraulic pump 55 being driven by an electric motor 56.
Check valves 57 and 58, which only permit brake fluid to flow from
the reservoir 53 side to the fluid paths Pb and Qb side, are
disposed on the intake side and the discharge side of each
hydraulic pump 55. Furthermore, check valves 59, which only permit
brake fluid to flow from the fluid paths Pc and Pd; Qc and Qd side
to the fluid paths Pb and Qb side, are connected in parallel to
each in-valve 62.
Connected to the fluid path Pa is a first fluid pressure sensor Sa
for detecting the fluid pressure thereof, and connected to the
fluid path Qb is a second fluid pressure sensor Sb for detecting
the fluid pressure thereof. The first fluid pressure sensor Sa, the
second fluid pressure sensor Sb, and wheel speed sensors Sc for
detecting the wheel speed of each wheel are connected to an
electronic control unit, which is not illustrated, that is
connected to the first and second master cut valves 32 and 33, the
simulator valve 34, the communication control valve 41, the slave
cylinder 42, and the hydraulic modulator 23.
The operation of the mode for carrying out the present invention
having the above-mentioned arrangement is now explained.
First, normal braking operation in a normal situation is explained
by reference to FIG. 2.
In a normal situation when the system is functioning normally, when
the first fluid pressure sensor Sa provided in the fluid path Pa
detects the brake pedal 12 being depressed by the driver, the first
and second master cut valves 32 and 33, which are normally open
electromagnetic valves, are energized and thus close, the simulator
valve 34, which is a normally closed electromagnetic valve, is
energized and thus opens, and the communication control valve 41,
which is a normally closed electromagnetic valve, is energized and
thus opens. At the same time as the above, the actuator 43 of the
slave cylinder 42 operates and the piston 48 moves forward, thereby
generating a brake fluid pressure in the fluid pressure chamber 50.
Since at this time the communication control valve 41, which is a
normally closed electromagnetic valve, is energized and thus opens,
the brake fluid pressure generated by the slave cylinder 42 is
transmitted to the fluid path Pb and the fluid path Qb connected to
the fluid path Pb via the third fluid path Rc, and is transmitted
from the two fluid paths Pb and Qb to the wheel cylinders 26 and
27; 30 and 31 of the disk brake devices 24 and 25; 28 and 29 via
the opened in-valves 52 of the hydraulic modulator 23, thus braking
each wheel.
Furthermore, the brake fluid pressure generated by the first fluid
pressure chamber 17 of the master cylinder 11 is transmitted to the
fluid pressure chamber 39 of the stroke simulator 35 via the opened
simulator valve 34 to move the piston 38 against the spring 37,
thus allowing a stroke of the brake pedal 12 and generating a
simulated pedal reaction force to eliminate any disagreeable
sensation for the driver.
Controlling the operation of the actuator 43 of the slave cylinder
42 so that the brake fluid pressure due to the slave cylinder 42
detected by the fluid pressure sensor Sb provided in the fluid path
Qb has a magnitude corresponding to the brake fluid pressure due to
the master cylinder 11 detected by the fluid pressure sensor Sa
provided in the fluid path Pa enables a braking force corresponding
to the amount of operation inputted by the driver into the brake
pedal 12 to be generated in the disk brake devices 24 and 25; 28
and 29.
Furthermore, when it is desired to make the brake fluid pressure
transmitted to the wheel cylinders 30 and 31 of the first line
(rear wheels) and the brake fluid pressure transmitted to the wheel
cylinders 26 and 27 of the second line (front wheels) transiently
different, the braking force of the front wheel can be made lower
than the braking force of the rear wheel by opening the
communication control valve 41 with a variable degree of opening at
any intermediate degree of opening.
Furthermore, in the case of a hybrid vehicle in which for example
the front wheels are driven by a motor/generator, control is
carried out by decreasing the fluid pressure braking force of the
front wheels connected to the motor/generator by an amount
corresponding to the braking force that is generated by
regenerative braking of the motor/generator when the vehicle is
decelerating, so that the total braking force is made to coincide
with a target value. In such a case, as described above,
controlling the communication control valve 41 at a predetermined
intermediate degree of opening enables the fluid pressure braking
force of the front wheels to be transiently reduced.
The operation of ABS control in a normal situation is now explained
by reference to FIG. 3.
During the above-mentioned braking in a normal situation, when
based on the output of the wheel speed sensors Sc it is detected
that the slip rate of a wheel has increased and there is a tendency
for it to lock, the operating state of the slave cylinder 42 is
maintained, and in this state the hydraulic modulator 23 is
operated to thus prevent the wheel from locking
That is, when there is a tendency for the predetermined wheel to
lock, in a state in which the in-valve 52 communicating with the
wheel cylinder of the disk brake device of the wheel is closed and
transmission of brake fluid pressure from the slave cylinder 42 is
blocked, a pressure decrease operation in which the out-valve 54 is
opened to thus release the brake fluid pressure of the wheel
cylinder to the reservoir 53 and subsequently a maintenance
operation in which the out-valve 54 is closed to thus maintain the
brake fluid pressure of the wheel cylinder are carried out, thus
decreasing the braking force so that the wheel does not lock.
If, as a result, the wheel speed recovers and the slip rate
decreases, a pressure increase operation in which the in-valve 52
is opened to thus increase the brake fluid pressure of the wheel
cylinder is carried out, thereby increasing the braking force on
the wheel. If the wheel again has a tendency to lock due to this
pressure increase operation, the above-mentioned pressure decrease,
maintenance, and pressure increase are carried out again, and
repeating them enables the maximum braking force to be generated
while suppressing locking of the wheel. In this process, brake
fluid that has flowed into the reservoir 53 is returned to the
fluid paths Pb and Qb on the upstream side by means of a hydraulic
pump 55.
FIG. 3 shows a state in which the brake fluid pressure of the wheel
cylinder 26 of the left rear wheel is maintained, the brake fluid
pressure of the wheel cylinder 27 of the right rear wheel is
decreased, and the brake fluid pressure of the wheel cylinders 30
and 31 of the left and right front wheels are increased.
The operation of VSA control in a normal situation is now explained
by reference to FIG. 4.
VSA control achieves stability of behavior by making the braking
force of the inner turning wheel different from the braking force
of the outer turning wheel to thus generate a yaw moment, and
preventing lateral slip of the vehicle by this yaw moment. There is
the difference that whereas ABS control is carried out only when
braking, VSA control is also carried out when the vehicle is
turning even if not accompanied by braking. In the present
embodiment, control based on the operation of VSA is shown as a
mode for carrying out pressure increase/pressure decrease control
independently for four wheels, but the mode for carrying out
pressure increase/pressure decrease control independently for four
wheels is not limited to the time when VSA is being carried out.
The operation of pressure decrease, maintenance, and pressure
increase of the brake fluid pressure transmitted to the wheel
cylinders 26 and 27; 30 and 31 of respective wheels is the same as
that of the above-mentioned ABS control, but since it is possible
to control the pressure by controlling the amount of drive of the
slave cylinder 42 in normal VSA control, the pressure increase
function of the hydraulic pumps 55 and 55 can be omitted, and they
may have only the function of circulation.
FIG. 4 shows a state in which the brake fluid pressure of the wheel
cylinder 26 of the left rear wheel is maintained, the brake fluid
pressure of the wheel cylinder 27 of the right rear wheel and the
wheel cylinder 31 of the right front wheel is decreased, and the
brake fluid pressure of the wheel cylinder 30 of the left front
wheel is increased.
The operation when a malfunction such as liquid leakage occurs in
the wheel cylinders 26 and 27 of the first line or the wheel
cylinders 30 and 31 of the second line is now explained by
reference to FIG. 5.
In a case in which a malfunction such as liquid leakage occurs in
at least one of the wheel cylinders 26 and 27 of the left and right
rear wheels (first line) when the system is normal, in an
arrangement in which all of the wheel cylinders 26 and 27; 30 and
31 of first and second lines are operated by a slave cylinder 42
having only a single fluid pressure chamber 50, there is a
possibility that the braking force will be lost completely due to
the liquid leakage.
In the present embodiment, in a state in which communication
between the malfunctioning wheel cylinders (in FIG. 5 either the
wheel cylinders 26 and 27 of the first line or the wheel cylinders
30 and 31 of the second line) is blocked by closing the
communication control valve 41 and the first master cut valve 32 is
closed, the second master cut valve 33 is opened. Because of this,
the brake fluid pressure from the master cylinder 11 independently
acts on the fluid path Qb, and the brake fluid pressure from the
slave cylinder 42 independently acts on the fluid path Pb; even if
one of the wheel cylinders 26 and 27 of the first line or the wheel
cylinders 30 and 31 of the second line malfunctions, the braking
force can be ensured by operating the other without any
problems.
The operation when the slave cylinder 42 becomes inoperable due to
a malfunction of a power supply, etc. is now explained by reference
to FIG. 6.
When the power supply malfunctions, the first and second master cut
valves 32 and 33, which are normally open electromagnetic valves,
automatically open, the simulator valve 34 and the communication
control valve 41, which are normally closed electromagnetic valves,
automatically close, the in-valves 52, which are normally open
electromagnetic valves, automatically open, and the out-valves 54,
which are normally closed electromagnetic valves, automatically
close. In this state, the brake fluid pressure generated in the
first and second fluid pressure chambers 17 and 19 of the master
cylinder 11 passes through the first and second master cut valves
32 and 33 and the in-valves 52 without being absorbed by the stroke
simulator 35, to thus operate the wheel cylinders 26 and 27; 30 and
31 of the disk brake devices 24 and 25; 30 and 31 of the wheels,
and a braking force can be generated without problems.
In this process, if the brake fluid pressure generated by the
master cylinder 11 acts on the fluid pressure chamber 50 of the
slave cylinder 42 and makes the piston 48 move backward, there is a
possibility that the volume of the fluid pressure chamber 50 will
expand and the pressure of the brake fluid pressure will decrease;
if an attempt is made to maintain the brake fluid pressure the
stroke of the brake pedal 12 will increase. However, in accordance
with the present embodiment, since backward movement of the ball
screw mechanism 46 of the slave cylinder 42 is suppressed if a load
from the piston 48 side is inputted, any increase in the volume of
the fluid pressure chamber 50 is suppressed. A member for
restricting backward movement of the piston 48 may be provided
separately for when the slave cylinder 42 malfunctions. In this
case, a structure in which drive resistance is not increased during
normal operation is desirable.
Furthermore, when the power supply malfunctions, since the
communication control valve 41 is closed, the fluid paths Pa to Pd
of the first line and the fluid paths Qa to Qd of the second line
are completely separated; even if the fluid path of one line
suffers from a liquid leakage malfunction, the braking force of the
other line can be maintained, and redundancy can be further
enhanced.
If the power supply malfunctions in a state in which the brake
pedal 12 is depressed, the simulator valve 34, which is a normally
closed electromagnetic valve, automatically closes to trap the
brake fluid in the stroke simulator 35; there is a possibility that
the volume of brake fluid will become insufficient, but since in
such a case the brake fluid of the stroke simulator 35 passes
through the check valve 40 and is returned to the master cylinder
11 side, no problem occurs.
As hereinbefore described, in accordance with the present
embodiment, when the system is normal, in a state in which the
first and second master cut valves 32 and 33 are closed and the
simulator valve 34 is opened, the communication control valve 41 is
opened so as to connect to the slave cylinder 42 both the first and
second fluid paths Pb to Pd; Qb to Qd connected to each other via
the third fluid path Rc, thereby operating the wheel cylinders 26,
27; 30 and 31 of the first and second lines by means of brake fluid
generated by the slave cylinder 42 while enabling stroke of the
brake pedal 12 by means of the stroke simulator 35. This enables
the slave cylinder 42 having only the single fluid pressure chamber
50 to be used instead of a tandem type slave cylinder, thus
simplifying the structure of the brake device.
Furthermore, when the slave cylinder 42 becomes inoperable due to a
malfunction of the power supply, opening the first and second
master cut valves 32 and 33 and closing the communication control
valve 41 enables the wheel cylinders 26 and 27; 30 and 31 of the
first and second lines respectively to be operated by means of the
brake fluid pressure generated by the first and second fluid
pressure chambers 17 and 19 of the master cylinder via the first
and second fluid paths Pa to Pd; Qa to Qd. Moreover, in this
process, since the communication control valve 41 is closed so as
to block the interconnection between the first and second fluid
paths Pa to Pd; Qa to Qd, when there is a malfunction such as
liquid leakage in the wheel cylinders 26 and 27; 30 and 31 of one
of the first and second lines, the operation of the wheel cylinders
26 and 27; 30 and 31 of the other line is enabled to thus ensure
the braking force.
Furthermore, since the hydraulic modulator 23 is disposed on the
downstream side relative to the third fluid path Rc, controlling
the opening and closing of the in-valves 52 enables the brake fluid
pressure generated by the slave cylinder 42 to be freely adjusted
and independently supplied to the wheel cylinders 26 and 27; 30 and
31.
Moreover, since the out-valves 54, which can release the brake
fluid pressure from the slave cylinder 42 to the reservoir 53, are
provided on the downstream side relative to the in-valves 52 of the
hydraulic modulator 23, any brake fluid pressure generated by the
slave cylinder 42 can be decreased individually by opening the
out-valves 54 and transmitted to each of the wheel cylinders 26 and
27; 30 and 31, and this enables the brake fluid pressure acting on
each of the wheel cylinders 26 and 27; 30 and 31 to be
independently controlled, thus giving ABS operation or VSA
operation.
Furthermore, if brake fluid pressure from the master cylinder 11 is
applied to the fluid pressure chamber 50 of the slave cylinder 42
when there is an abnormality of the system, since expansion of the
volume of the fluid pressure chamber 50 is restricted by the ball
screw mechanism 46, it is possible to suppress any decrease in the
slave cylinder 42 of the brake fluid pressure generated by the
master cylinder 11.
Moreover, since the degree of opening of the communication control
valve 41 can be adjusted, it is possible to decrease the brake
fluid pressure transmitted to the second fluid path Qb to Qd
connected to the first fluid path Pb to Pd via the communication
control valve 41 relative to the brake fluid pressure generated by
the slave cylinder 42 and transmitted to the first fluid path Pb to
Pd, thus making the brake fluid pressures acting on the wheel
cylinders 26 and 27; 30 and 31 of the first and second lines
transiently different.
Furthermore, since there are provided the first fluid pressure
sensor Sa for detecting the brake fluid pressure generated by the
master cylinder 11 and the second fluid pressure sensor Sb for
detecting the brake fluid pressure of the fluid path Qb between the
second master cut valve 33 and the in-valves 52, the first fluid
pressure sensor Sa is disposed in the first fluid path Pa to Pd
directly connected to the slave cylinder 42, and the second fluid
pressure sensor Sb is provided not in the first fluid path Pa to Pd
directly connected to the slave cylinder 42 but in the second fluid
path Qa to Qd connected to the slave cylinder 42 via the
communication control valve 41, when the communication control
valve 41 is opened to provide communication between the first and
second fluid paths Pa to Pd; Qa to Qd and when the communication
control valve 41 is closed to block the connection between the
first and second fluid paths Pa to Pd; Qa to Qd, it is possible to
detect abnormalities of the first master cut valve 32 and the
communication control valve 41 based on values detected by the
first and second fluid pressure sensors Sa and Sb.
A mode for carrying out the present invention is explained above,
but the present invention may be modified in a variety of ways as
long as the modifications do not depart from the spirit and scope
thereof.
For example, the brake device of the embodiment is provided with
the hydraulic modulator 23, but the present invention may also be
applied to a brake device that is not provided with the hydraulic
modulator 23.
Furthermore, in the embodiment, the slave cylinder 42 is controlled
based on a value detected by the first fluid pressure sensor Sa,
but the slave cylinder 42 may be controlled based on an amount of
operation of the brake pedal 12 detected by a stroke sensor.
Moreover, in the embodiment, the wheel cylinders 26 and 27 of the
left and right rear wheels are defined as the first line, and the
wheel cylinders 30 and 31 of the left and right front wheels are
defined as the second line, but the wheel cylinder 30 of the left
front wheel and the wheel cylinder 27 of the right rear wheel may
be defined as the first line, and the wheel cylinder 31 of the
right front wheel and the wheel cylinder 26 of the left rear wheel
may be defined as the second line, or the wheel cylinders 30 and 31
of the left and right front wheels may be defined as the first
line, and the wheel cylinders 26 and 27 of the left and right rear
wheels may be defined as the second line.
* * * * *